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    Re: nautical almanac first point of aries
    From: Geoffrey Kolbe
    Date: 2012 Mar 12, 21:26 +0000

    In a sidereal reference frame,  the earth rotates 15 degrees 2.5
    minutes in one hour,  not 15 degrees dead....
    
    Just out of interest, my Long Term Almanac predicts a GHA angle of 80
    degrees 46.9 minutes for 1800 hrs today. Not bad, considering I
    compiled it 13 years ago now.
    
    Geoffrey Kolbe
    
    
    At 18:17 12/03/2012, you wrote:
    >Greetings,
    >
    >I have been looking at the online nautical almanac at
    >http://www.tecepe.com.br/scripts/AlmanacPagesISAPI.isa/pages?date=03/12/2012
    >
    >and for today  monday  12 mar 2012  the GHA angle for aries  is  80
    >deg 47.1 min  at  18:00 h  GMT
    >
    >I think  I can convert the GHA for aries to  time  and that should be the
    >same as sidereal time at Greenwich.
    >
    >(  (80./15) + (47.1/60)/15 ) =  5.38566...
    >taking the 5 out and mult the fractional part by 60         .3856666 *
    >60 = 23.1399...
    >and taking out the 23   and doing the same                    .13999
    >* 60 = 8.3
    >
    >I used this web site to get sidereal time at  longitude 0 deg 0 min
    >http://tycho.usno.navy.mil/cgi-bin/sidereal-post.sh
    >and pressed compute at approx.  16:00:00   GMT
    >
    >05:23:45.4
    >
    >
    >The seconds are not in close enough agreement which makes me think I am
    >missing something or have made an error in the computations?
    
    
    
    
    

       
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